Evolution of the Genes Encoding Starch Synthase in Sorghum and Common Wheat

Abstract

Starch synthases (SSs) play important roles in plant starch synthesis. Five enzymetic isoforms of starch synthases have been found in plant, some of isoforms have further diverged possibly via whole genome duplication events, which might result in two or three subclasses of the sequences in rice and maize. In this study, we found the retention of GBSS, SSII, and SSIII duplicators except for the SSIV duplicator in genomes of sorghum and wheat. The SSIV gene might have been lost in maize and sorghum genomes based on the synteny relationship among rice maize and sorghum. Expression analyses indicated that the SS duplicators were also diverged from the duplicators of SbGBSSI, SbSSIIIa in expression pattern, and SbSSIIa were expressed mainly in endosperm in sorghum, whereas SbGBSSII, SbSSIIb, and SbSSIIIb of sorghum, TaSSIIb and TaSSIIIb of common wheat, were expressed mainly in leaves. Our findings, in combination with previous studies, indicate that the SSIV duplicator should be not remained in all Gramineae species, while the expression of duplicated SS genes diverged similarly in the studied species.